Abstract

In this paper, the network planning problem in wireless ad hoc networks is formulated as the problem of allocating physical layer resources, or supplies, to minimize a cost function while fulfilling certain end-to-end communication demands, which are given as a collection of multicast sessions with desired transmission rates. We propose an iterative cross-layer optimization, which alternates between 1) jointly optimizing the timesharing in the link layer and the flow assignment in the network layer, and 2) updating the operational states in the physical layer. We consider two objectives, minimizing aggregate congestion and minimizing power consumption, respectively corresponding to operating in a bandwidth-limited regime and in an energy-limited regime. The end result is a set of achievable tradeoffs between throughput and energy efficiency, in a given wireless network with a given traffic pattern. We evaluate our cross-layer approach quantitatively by simulations of community wireless networks, and compare with designs that decouple the layers. We demonstrate that significant performance advantages, in terms of congestion reduction and energy efficiency, can be achieved by adopting a full-fledged cross-layer optimization. Furthermore, we observe that optimized solutions generally profit from network coding, physical-layer broadcasting, and traffic-dependent physical states.